Problem: Simplify the following expression: $n = \dfrac{6t}{7} - \dfrac{3t}{2}$
Answer: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $7$ and $2$ $\lcm(7, 2) = 14$ $ n = \dfrac{2}{2} \cdot \dfrac{6t}{7} - \dfrac{7}{7} \cdot \dfrac{3t}{2} $ $n = \dfrac{12t}{14} - \dfrac{21t}{14}$ $n = \dfrac{12t -21t}{14}$ $n = \dfrac{-9t}{14}$